Pulverulent alloy



UNITED STATES PATENT OFFICE PULYERULENT ALLOY Leo Schlecht and AlbertHelnzel, Ludwigshafenon-the-Rhine, Germany, minors to I. G.Farbenindustrie Aktiengesellschaft, Frankforton-the-Main, Germany NoDrawing. Application January 19,1934, lsg-al' No. 707.339. In GermanyJan 24 17 Claims. (01. 75-122) The present invention relates to aprocess of der; it is often preferable to use other comproducingpulverulent alloys of metals capable pounds, for example nitrates whichon heating of forming metal carbonyls. yield the substances hinderingthe fritting to-'v Pulverulent alloys, as for example of iron withgether". When working in a non-reducing atnickel, cobalt, chromium,molybdenum or tungmosphere the substances hindering the fritting sten,have hitherto usually been obtained by metogether may be prepared fromthe metals to chanical comminution of compact alloys. This be alloyed byslightly oxidizing the metal powder method of working is lengthy andcostly because itself precedent to the heat treatment giving as a rulesuch alloys are very tough, especially rise to the desired alloyformation.

when they contain no carbon and oxygen. More- The addition substancesare preferably mixed 10 over, the particles of powder readily becomeconas intimately as possible with the mixture of taminated withundesirable foreign substances; the pulverulent metals derived fromcarbonyls. their shape, also, is not uniform. A very intimate mixing isobtained for example We have now found that pulverulent alloys of bygrinding the dry or wet mixture in a ball mill l5 metals formingcarbonyls are obtained in an esor by making into a paste and trituratingthe pecially advantageous manner by thermally demetal powder with asolution or suspension of composing a mixture of the carbonyls of thedethe addition materials, as for example with a sired alloyconstituents, coating the particles of i n of m n sium or aluminiumnitrate. the resulting metal powder with a substance Small amounts ofadditional substances, as for hindering the fritting together thereofand then example less than 1 per cent, are usually sum- 20 heating thecoated powder in a no oxidizing, cient to prevent the agglomerationofthe pari. e. an inert or reducing atmosphere so that alloy ticles.

formation takes place by diffusion within the If it is desired to removethe additional subparticles of the metal powder without smelting.stances from the metal powder after the heat- The thermal decompositionof the carbonyl ing, substances are chosen which are capable of 25mixture, which is employed for example in the subsequent removal bydissolution, as for exform of a mixture of two or more liquid or solidample with dilute acids, by frothing or by magmetal carbonyls, or asolution thereof, for exnetic separation in conjunction withwind-siftample a solution of one or more solid metal caring.

bonyls in one or more liquid metal carbonyls, and Temperatures above 500C. are suitable for 30 atomized or vaporized into the decomposition theheating of the metal powders with the addichamber, is preferably carriedout at temperation substances for the purpose of forming altures below450 C. in order to avoid too strong loys; at temperatures below 500 0.,the formaa deposition of carbon. To produce the most tion of alloysusually takes place incompletely uniform distribution possible of thecarbonyl and very slowly. It is preferable to work be- 35 mixture, othergases, as for example carbon tween 900 and 1000 C. The duration ofheatmonoxide, carbon dioxide, nitrogen or ammonia, ing may be shorterthe higher the temperature may also be introduced into the decompositionemployed, and the smaller the size of the particles chamber, or themetal carbonyls may be atomized of the metal powder. It is especiallyadvantageby means of such gases. In particular, decompoous to carry outthe heating of the metal powders 40 sition in the hot free space of aheated vessel in a current of hydrogen because in this way the hasproved advantageous because globular pardiffusion within the particlesof the metal powticles of uniform size are thus obtained throughder isaccelerated by the simultaneous volatilizeout. The vessel may be heatedeither externally, tion of the carbon usually present.

or by introducing hot inert gases into the vessel, The resulting alloypowders are distinguished 45 if desired in counter-current to the metalcarby their purity and the globular shape of the bonyls introduced.single particles. The pulverulent alloys, espe- As coating substanceshindering fritting tocially powders of alloys of nickel-iron containinggether as previously mentioned, refractory subpreferably between 40 and80 per cent of nickel,

stances, as for example oxides of alkaline earth or nickel-iron-cobalt,in particular such as con- 50 metals, of magnesium, aluminium, berylliumand tain between 25 and 50 per cent of iron, between zinc and ceramicsubstances, silica, titanic acid 30 and 60 per cent of nickel andbetween 15 and other diflicultly fusible or diflicultly reducible and 30per cent of cobalt, or alloys of the latter compounds, are used. It isnot necessary to kind containing up to-10 per cent of molybadd thesecompounds as such to the metal powdenum or tungsten to increase theelectric re- 55 sistance, have very good magnetic properties andconsequently may be employed with special advantage for electromagneticpurposes, as for example ior the preparation of mass cores for Pupincoils or in the radio industry. When preparing alloys intended forelectromagnetic purposes, the hydrogen treatment for decarbonizing thepowder is preferably carried on until the carbon content of the powderhas fallen to 0.04 per cent or less.

Sometimes it may happen that the mass obtained in the manner describedslightly coheres. In such cases merely a slight mechanical treatment,for example by shaking or if desired grinding for a short time willproduce the pulverulent alloy aimed at.

The following example will further illustrate the nature of thisinvention but the invention is not restricted to this example. The partsare by weight.

Example 20 parts of a nickel-iron powder, consisting of 41.8 per cent ofnickel, 1.4 per cent of carbon and the remainder iron, which has beenobtained by the thermal decomposition of a mixture of nickel carbonyland iron carbonyl in the hot free space of a heated vessel, are madeinto a paste with a solution of 1.2 parts of aluminium nitrate in 4parts of water. The resulting mass is heated for 12 hours at 1000 C. ina stream of hydrogen. The aluminium nitrate is thus converted intoaluminium oxide and the carbon content of the powder is lowered to 0.04per cent. The frothy, easily friable mass obtained after the heating maybe readily converted into anextremely finely divided powder withglobular single particles by grinding in a ball mill. The ground productis heated again for about half an hour at 800 C. and then worked up intomass cores for Pupin coils in the usual manner.

What we claim is:--

i. A process for producing pulverulent alloys of metals capable offorming metal carbonyls which comprises heating a mixture of at leasttwo metal carbonyls at a temperature up to about 450 C. to decompose thecarbonyls, coating the metal particles of the resulting powder with asubstance hindering the fritting together and then heating the coatedpowder in a non-oxidizing atmosphere at a temperature sufliciently highto effect alloying by diffusion within the particles of the metal powderwithout smelting.

2. A process for producing pulverulent alloys of metals capable offorming metal carbonyls which comprises heating a mixture of at leasttwo metal carbonyls at a temperature up to about 450 C. to decompose thecarbonyls, coating the resulting powder with up to l per cent by weightof a substance hindering the fritting together and then heatingthecoated powder in a nonoxidizing atmosphere at a temperaturesufiiciently high to efiect alloying by diffusion within the particlesof the metal powder without smeltns.

3. A process for producing pulverulent alloys of metals capable offorming metal carbonyls which comprises heating a mixture of at leasttwo metal carbonyls at a temperature up to about 450 C. to decompose thecarbonyls, coating the resulting powder with a substance hindering thefritting together and then heating the coated powder in a non-oxidizingatmosphere at a temperature above 500 C. to effect alloying by diffusionwithin the particles of the metal powder without smelting.

4. A process for producing pulverulent alloys of metals capable offorming metal carbonyls which comprises heating a mixture of at leasttwo metal carbonyls at a temperature up to about 450 C. to decompose thecarbonyls, coating the resulting powder with a substance hindering thefritting together and then heating the coated powder in a non-oxidizingatmosphere at a temperature between about 900 C. and about 1000 C. toeifect alloying by diffusion within the particles of the metal powderwithout smelting.

5. A process for producing pulverulent alloys of metals capable offorming metal carbonyls which comprises heating a mixture of at leasttwo metal carbonyls at a temperature up to about 450 C. to decompose thecarbonyls, coating the resulting powder with a substance hindering thefritting together" and then heating the coated powder in a reducingatmosphere at a temperature above 500 C. to effect alloying by diffusionwithin the particles of the metal powder without smelting.

6. A process for producing pulverulent alloys of metals capable offorming metal carbonyls which comprises heating a mixture of at leasttwo metal carbonyls at a. temperature up to about 450 C. to decomposethe carbonyls, coating the resulting powder with a substance hinderingthe fritting together and then heating the coated powder in a hydrogenatmosphere at a temperature above 500 C. to effect alloying by diffusionwithin the particles of the metal powder without smelting and thusproducing an alloy with a carbon content of at the most 0.04 per cent.

7. A process for producing pulverulent alloys of metals capable offorming metal carbonyls which comprises heating a mixture of at leasttwo metal carbonyls at a temperature up to about 450 C. to decompose thecarbonyls, coating the resulting powder with a refractory substanceselected from the group consisting of the oxides of the alkaline earthmetals, magnesium and aluminium and then heating the coated powder in anon-oxidizing atmosphere at a temperature willciently high to effectalloying by diffusion within the particles of the metal powder withoutsmelting.

8. A process for producing pulverulent alloys of metals capable offorming metal carbonyls which comprises heating a mixture of at leasttwo metal carbonyls at a temperature up to about 450 C. to decompose thecarbonyls, mixing the resulting powder with up to 1 per cent by weightof a refractory substance selected from the group consisting of theoxides of alkaline earth metals, magnesium and aluminium and thenheating the resulting mixture in a hydrogen atmosphere at a temperaturebetween about 900 and about 1000 C. to efiect alloying by diffusionwithin the particles of the metal powder without smelting and thusproducing an alby with a carbon content of at the most 0.04 per cent.

9. A process for producing pulverulent alloys of metals capable offorming metal carbonyls which comprises heating a mixture of at leasttwo metal carbonyls at a temperature up to about 450 C. to decompose thecarbonyls, coating the resulting powder with at least one substancewhich on heating yields a substance hindering the fritting together andthen heating the coated powder in a non-oxidizing atmosphere atatemperature sumciently high to effect alloying by diii'usion within theparticles of the metal powder without smelting.

10. A process for producing pulverulent alloys 01' metals capable offorming metal carbonyls which comprises heating a mixture oi at leasttwo metal carbonyls at a temperature up to about 450 C. to decompose thecarbonyls, coating the resulting powder with at least one substancewhich on heating yields a substance hindering the fritting together" andthen heating the coated powder in a non-oxidizing atmosphere at atemperature above 500 C. to eiTect alloying by diffusion within theparticles of the metal powder without smelting.

11. A process for producing pulverulent alloys of metals capable 01'forming metal carbonyls which comprises heating a mixture of at leasttwo metal carbonyls at a temperature up to about 450C. to decompose thecarbonyls, coating the resulting powder with at least one substancewhich on heating yields a substance hindering the fritting together andthenheating the coated powder in a reducing atmosphere at a temperatureabove 500 C. to effect alloying by diii'usion within the particles ofthe metal powder without smelting.

12.v A process for producing pulverulent alloys of metals capable offorming metal carbonyls which comprises heating a mixture of at leasttwo metal carbonyls at a temperature up to about 450 C. to decompose thecarbonyls, coating the resulting powder with at least one substancewhich on heating yields a substance hindering the fritting together" andthen heating the coated powder in a hydrogen atmosphere at a temperaturebetween about 900 and about 1000 C. to eiiect alloying by diflusionwithin the particles of the metal powder without smelting and thusproducing an alloy with a carbon content of at the most 0.04 per cent.

13. A process for producing pulverulent alloys of metals capable offorming metal carbonyls which comprises heating a mixture of 'at leasttwo metal carbonyls at a temperature up to about 450 C. to decompose thecarbonyls, slight- 1y oxidizing the particles or the resulting metalpowder and then heating the powder in an inert atmosphere at atemperature sumciently high to effect alloying by diflusion within theparticles oi the metal powder without smelting.

14. A process for producing pulverulent alloys of metals capable offorming metal carbonyls 5 which comprises heating a mixture of at leasttwo metal carbonyls at a temperature up to about450 C. to decompose thecarbonyls, slightly oxidizing the particles 01' the resulting metalpowder and then heating the powder in an inert atmosphere at atemperature above 500 C. to effect alloying by diffusion within theparticles of the metal powder without smelting.

15. A process for producing pulverulent alloys of metals capable offorming metal carbonyls which comprises heating a mixture of-at leasttwo metal carbonyls at a temperature up to about 450 C. to decompose thecarbonyls, slightly oxidizing the particles of the resulting metalpowder and then heating the powder in an inert atmosphere at atemperature between about 900 and about 1000 C. to eil'ect alloying bydii'- fusion'within the particles of the metal powder without smelting.

16. A process for producing pulverulent alloys of metals capable offorming metal carbonyls which comprises heating a mixture of at leasttwo metal carbonyls at a temperature up to about 450 C. to decompose thecarbonyls, slightly oxidizing the particles 01' the resulting metalpowder and then heating the powder in a nitrogen atmosphere at atemperature suiliciently' high to efl'ect alloying by diilusion withinthe particles of the metal powder without smelting.

1'7. A process for producing pulverulent alloys of metals capable offorming metal carbonyls which comprises heating a mixture of at leasttwo metal carbonyls at a temperature up to about 450 C. to decompose thecarbonyls, slightly oxidizing the particles of the resulting metal 43powder and then heating the powder in a nitrogen atmosphere at atemperature between about 900 and 1000 C. to eii'ect alloying bydiflusion within the particles of the metal powder without smelting. 45-

LEO SCHLECHT. ALBERT

